Pulsed-based time of flight methods and system

Patent metadata

Field	Value
Publication number	US-10663565-B2
Application number	US-201715708268-A
Country	US
Kind code	B2
Filing date	Sep 19, 2017
Priority date	Sep 19, 2017
Publication date	May 26, 2020
Grant date	May 26, 2020

Abstract

A time of flight sensor device is provided that is capable of generating accurate information relating to propagation time of emitted light pulses using a small number of measurements or data captures. By generating pulse time of flight information using a relatively small number of measurement cycles, object distance information can be generated more quickly, resulting in faster sensor response times. Embodiments of the time of flight sensor can also minimize or eliminate the adverse effects of ambient light on time of flight measurement. Moreover, some embodiments execute time of flight measurement techniques that can achieve high measurement precision even when using relatively long light pulses having irregular, non-rectangular shapes.

First claim

What is claimed is:

1. A time of flight sensor device, comprising:
an emitter component configured to emit a light pulse at a first time during a measuring sequence;
a photo-sensor component comprising a photo-detector, the photo-detector comprising
a photo device configured to generate electrical energy in proportion to a quantity of received light,
a first measuring capacitor connected to the photo device via a first control line switch,
a second measuring capacitor connected to the photo device via a second control line switch, and
a third measuring capacitor connected to the photo device via a third control line switch,

wherein the photo-sensor component is configured to
set a first control signal of the first control line switch at a second time during the measuring sequence defined relative to the first time, and reset the first control signal at a third time, wherein setting the first control signal at the second time and resetting the first control signal at the third time causes a first portion of the electrical energy proportional to a leading portion of a received reflected light pulse corresponding to the light pulse emitted by the emitter component to be stored in the first measuring capacitor, and
set a second control signal of the second control line switch at the third time, wherein setting the second control signal at the third time causes a second portion of the electrical energy proportional to a trailing portion of the received reflected pulse to be stored in the second measuring capacitor; and

a distance determination component configured to
subtract a third measured value of a third portion of the electrical energy corresponding to ambient light stored on the third measuring capacitor from a first measured value of the first portion of the electrical energy and a second measured value of the second portion of the electrical energy to yield a leading pulse portion value and a trailing pulse portion value, respectively,
determine a ratio of the trailing pulse portion value to a total of the leading pulse portion value and the trailing pulse portion value, and
determine a propagation time for the light pulse based on a product of the ratio and a duration T 0 of the received reflected light pulse added to a duration Ts between a falling edge of the light pulse and the third time.

2. The time of flight sensor device of claim 1 , wherein
the photo-sensor component is further configured to, while the received reflected light pulse is not being received at the photo-detector, set a third control signal of the third control line switch for a duration equal to or substantially equal to a first duration of the first control signal and a second duration of the second control signal, wherein setting the third control signal for the duration causes the third portion of the electrical energy to be stored on the third measuring capacitor.

3. The time of flight sensor device of claim 2 , wherein the distance determination component is configured to determine the propagation time based on

t
p

=

α
⁢

⁢
V
⁢

⁢
2

-

β
⁢

⁢

V
A

V
⁢

⁢
1

+

∝

V
⁢

⁢
2

-

2
⁢

⁢
β
⁢

⁢

V
a

⁢

T
0

+

T
S

where tp is the propagation time, T 0 is the duration of the received reflected light pulse, V 1 is the first measured value, V 2 is the second measured value, V A is the third measured value, Ts is the duration between the falling edge of the light pulse and the third time, β is a first compensation factor based on a mismatch between the third measuring capacitor and the first measuring capacitor, and α is a second compensation factor based on a capacitance mismatch between the first measuring capacitor and the second measuring capacitor.

4. The time of flight sensor device of claim 3 , wherein
the light pulse is a first light pulse,
the received reflected light pulse is a first received reflected light pulse,
the emitter component is further configured to emit a second light pulse at a fourth time during a first part of a calibration sequence and a third light pulse at a fifth time during a second part of the calibration sequence,
the photo-sensor component is further configured to:
during the first part of the calibration sequence:
set the first control signal at a sixth time defined relative to the fourth time, and reset the first control signal at a seventh time, wherein setting the first control signal at the sixth time and resetting the first control signal at the seventh time causes a fourth portion of the electrical energy proportional to a leading portion of a second received reflected light pulse corresponding to the second light pulse to be stored in the first measuring capacitor, and
set the second control signal at the seventh time, wherein setting the second control signal at the seventh time causes a fifth portion of the electrical energy proportional to a trailing portion of the second received reflected pulse to be stored in the second measuring capacitor,
measure and store the fourth portion as a fourth measured value V 1 a , and
measure and store the fifth portion as a fifth measured value V 2 a , and during the second part of the calibration sequence:
set the first control signal at an eighth time defined relative to the fifth time, and reset the first control signal at a ninth time, wherein setting the first control signal at the eighth time and resetting the first control si

Assignees

• Rockwell Automation Tech Inc

Inventors

• Boutaud Frederic
• Li Mei

Classifications

• G01S17/10

  using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) · CPC title

• G01S7/4865 Primary

  Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487) · CPC title